Welding torches used in TIG (tungsten inert gas) and GTAW (gas tungsten arc welding) are of two general types: air or gas cooled; and water cooled. The air or gas cooled welding torches are generally employed in lighter duty applications and are cooled solely by dissipating the heat buildup in the torch to the surrounding air. A slight cooling effect is provided by the shielding gas passing through the torch and as a result, such torches are sometimes referred to as gas cooled torches. Water cooled models are used for heavier duty welding applications where the heat buildup in the torch is removed by circulating cooling water through the torch head and service lines.
In both water and air cooled torch assemblies, the line that conveys the electrical output from the power source or welding machine to the torch head is referred to as the power cable. In water cooled torches, the power cable also conveys the cooling water from the torch head back to a circulator reservoir. In air cooled torch assemblies, the power cable also provides a dual function. Instead of conveying cooling water back to the circulator reservoir, the power cable conveys an inert shielding gas, such as argon, to the torch head about the conductor which is generally formed of a stranded copper cable. The cable is attached to metallic connectors made of copper or brass that are attached to the ends of the outer hose or tube. The connectors are typically threaded for threadably engaging the welding torch head at one end and the welding machine at the other end so as to conduct the output power of the welding machine to the welding torch head. The cable connectors also have an aperture therein so as to allow for the passage of the inert shielding gas therethrough and into the hose or tube about the cable such that the gas can pass therethrough to the torch head. The copper cable is smaller in diameter than the bore of the outer tube or hose so that the gas can pass alongside the copper cable.
Several years ago, the outer hose or tube portions of these power cables were made from extruded plastic materials, typically polyvinylchloride (PVC). They were light in weight and flexible but were short lived due to the harsh environment of a welding shop. The heat buildup from the copper cable during use caused the tube to soften and the pressure of the shielding gas passing within the tube would often balloon and burst the tube. The plastic tube was also easily damaged by contact with sparks or other hot materials around the welding site. The plastic tubes also were easily cut by any sharp edges of the materials being welded and in cold weather, they were stiff and hard. Plastic tubes also tended to stiffen with age. As a result of these shortcomings, the industry turned to the use of rubber hoses for their increased durability.
This next generation of power cable typically comprise an inner extruded rubber tube, a layer of fabric reinforcement disposed about the inner tube and an outer layer of rubber covering. The three elements were bonded together to form a hose assembly which was very durable and resistant to high pressures. Such hoses were also cost effective and as a result, replaced the PVC tube power cables. This hose construction, however, rendered the power cable relatively stiff and heavy. The stiffness significantly reduced the bend radius of the power cable and since the TIG welding process is a very articulate process requiring precision torch movement by the welder, these heavy, stiff power cables made the welder's job more difficult and tiring.
In an attempt to regain the flexibility of the earlier cables while retaining reasonable durability, a new power cable configuration which was developed which comprised an extruded rubber inner tube and a braided fabric cover. The inner rubber tube portion of the cable was soft, flexible and light in weight and the outer braid, usually of nylon, provided strength against ballooning and some abrasion resistance. However, during the welding process, the power cable and other lines are continually dragged about the shop floor and are subjected to sparks, hot metals and sharp edges. The outer fabric braided covers on the power cables proved to provide inadequate abrasion resistance. This problem was particularly acute with the power cables used with air or gas cooled welding torches as the power cable is not protected. In water cooled welding systems, three or more lines connect the torch to the power supply and three lines are generally bundled together within an elongated protective cover. The power cables in air and gas cooled systems are not covered and are unprotected during use. It would be highly desirable to provide a new power cable construction for air and gas cooled welding torches which maintained the lightweight and flexibility of the existing cables but which also provided the abrasion resistance and overall durability of earlier rubber hose power cables. The improved power cable of the present invention achieves this result.